In the present work experimental and numerical modeling studies of the heterogeneously catalyzed and electrochemical oxidation of CO at Nickel/yttria-stabilized zirconia (YSZ) solid oxide fuel cell (SOFC) anode systems were performed to evaluate elementary charge-transfer reaction mechanisms taking place at the three-phase boundary of CO/CO gas-phase, Ni 2electrode, and YSZ electrolyte. Temperature-programmed desorption and reaction experiments along with density functional theory calculations were performed to determine adsorption/desorption and surface diffusion kinetics as well as thermodynamic data for the CO/CO /Ni and CO/CO /YSZ systems. Based on these data elementary reaction based models 2 2with four different charge transfer mechanisms for the electrochemical CO oxidation were developed and applied in numerical simulations of literature experimental electrochemical data such as polarization curves and impedance spectra. Comparison between simulation and experiment demonstrated that only one of the four charge transfer mechanisms can consistently reproduce the electrochemical data over a wide range of operating temperatures and CO/CO gas 2compositions.

Acknowledgements There are many people who deserve credit and thanks for their part in this thesis. Without their contributions and support, this work would not have been possible. I wish to express my sincere gratitude to all my research advisors. First and foremost, I am most thankful to Priv.-Doz. Dr. Wolfgang Bessler for being an outstanding supervisor and mentor. Prof. Dr. Hans-Robert Volpp, my supervisor at PCI, for his indulgence and staying in the institute to the late night helping me in my work. I would like to thank the International Graduate College (IGK 710) “Complex Processes: Modeling, Simulation and Optimization” at the University of Heidelberg for fellowships. I have had the great pleasure of working with many talented and friendly people Marcel Vogler, Dzmitry Starukhin, Alexandr Gorski, Christian Hellwig, Nicolas Bayer-Botero, Stefan Gewies whose support and faithful discussion played irreplaceable role in my work. The individual thanks are due to Dr. Marcel Vogler who has been a tremendous help in working with calculation programs, Dzimitry Starukhin who has helped me with technical problems and made all the tools available to me that I needed to fix or construct equipments in lab, Dr. Alexandr Gorski for his extreme help with DFT calculations. I would like to thank my parents, Volodymyr and Galyna who have inspired me throughout my entire life to work hard, invest in myself through education, and to strive to be a good person. Finally, I would like to thank my wife, Viktoriya for her unending love, encouragement, and understanding.